In his inaugural address in December, 1852, President Henry P. Tappan appealed to the people of Michigan to take an interest in and to support the University. At the conclusion of his address Henry N. Walker, a prominent citizen of Detroit, asked the President how he might be of service, and Tappan suggested the raising of funds for an astronomical observatory.

A meeting was held in Detroit on December 29, 1852, for consideration of this project. Tappan and others spoke in favor of it, with the result that the sum of $7,000 was raised immediately, the Honorable Henry N. Walker, General Lewis Cass, Henry Porter Baldwin, later Governor of Michigan, and Senator Zachariah Chandler, each subscribing $500, on condition that an additional $10,000 be obtained from other sources within a year. Walker took a leading part in the drive for funds, which eventually amounted to about $15,000, of which he gave $4,000. In honor of the citizens of Detroit, whose initial gifts made it possible, the Observatory was named "Detroit Observatory," and this name was used until 1931. The original building and instruments cost $22,000, of which $7,000 was supplied by the Board of Regents from University funds. Subsequently, the citizens of Ann Arbor contributed $2,500 and those of Detroit $3,000 for needed improvements.

In March, 1853, while President Tappan was in Europe, mainly in the interest of the Observatory, Walker, acting in concurrence with him, made arrangements with George Bird, of New York, to superintend the construction of the Observatory Building. Four acres of land, outside the city, on a hill overlooking the valley of the Huron River, were purchased as a site, at a cost of $100 per acre. The Regents in November, 1853, authorized the purchase of the remainder of the site for the Observatory, which was completed in the summer of 1854.

The building is used entirely by the Department of Astronomy. The central part is 33 feet square, and there are two wings, each 19 by 29 feet. The central part is surmounted by a revolving dome 21 feet in diameter and contains the pier for the 12-inch refractor. The east wing was designed for the meridian circle instrument and the west wing for a library and an office for the director.

A residence for the Director, added at the west side of this building in 1868, was considerably enlarged and improved in 1905-6. It connected with the Observatory through the library. What is now the principal building of the Observatory was begun in 1908 and completed in the following year, with the exception of such parts of the dome as could not be finished until the large reflecting telescope was installed. It joins the meridian circle room of the old original Observatory on the east in the same manner that the residence joined the library on the west, and has a frontage of 44 feet on the north, and is 112 feet from north to south. It ends at the south in a circular wall, 43 feet high, which supports the dome of the large reflecting telescope. The building has two stories and a basement, which is practically above the level of the ground. On the main floor are the offices of the Director and Secretary, a classroom, clockroom, vault, and entrance and main halls. On the second floor are four offices and a darkroom. The basement contains rooms for laboratory, offices, and shop.

The dome for the reflecting telescope is 40 feet in diameter and has a slit eight and a half feet in width, which extends from the horizon of the instrument to a point two feet beyond the zenith. The base plate is made of heavy castings, carefully planed and fitted, and rigidly bolted together, to form a complete circle. The dome is covered with heavy copper plate, which is fastened directly to the steel frame. A double shutter closes the slit. It is opened and closed by an endless rope passing over a sheave, connected with the gears and cables which form the shutter-operating mechanism. The two halves of the shutter open and close simultaneously, and move parallel to each other.

The dome was constructed and erected by the Russell Wheel and Foundry Company of Detroit. This company, however, did not take care of the wheel work nor provide the guide rolls and the mechanism for turning the dome and for opening and closing the shutters. This was done by the Observatory instrument makers.

For the present main building and instruments, the Regents appropriated $15,000 in June, 1906, and an additional $25,000 later. This is the sum of two or more additional appropriations at unspecified dates previous to completion of the 37 ?-inch reflector in 1911, including a part of the cost of the telescope itself, as well as of the building. Much of the cost of the 37 ?-inch reflector does not appear as such, since it was in the form of labor, paid for in the salaries of the instrument-maker, H. J. Colliau, and his assistants.

The building contains the 12-inch refracting telescope and the meridian circle instrument, which have been continuously in operation since their installation in the 1850's.